1. The Field of the Invention
The present invention relates generally to the manufacture of carbon nanostructures using templating nanoparticles. More particularly, the present invention relates to methods for manufacturing nanomaterials that include carbon nanostructures and have minimal surface functional groups.
2. The Related Technology
Carbon materials have been used in a variety of fields as high-performance and functional materials. Pyrolysis of organic compounds is well-known to be one of the most useful methods to prepare carbon materials. For example, carbon materials can be produced by pyrolyzing resorcinol-formaldehyde gel at temperatures above 600° C.
Most carbon materials obtained by pyrolysis of organic compounds at temperatures between 600-1400° C. tend to be amorphous or have a disordered structure. Obtaining highly crystalline or graphitic carbon materials can be very advantageous because of the unique properties exhibited by graphite. For example, graphitic materials can be conductive and form unique nanomaterials such as carbon nanotubes. However, using existing methods it is difficult to make these well-crystallized graphite structures using pyrolysis, especially at temperatures less than 2000° C.
To acquire the graphitic structure at lower temperature many studies have been carried out on carbonization in the presence of a metal catalyst. The catalyst is typically a salt of iron, nickel, or cobalt that is mixed with carbon precursor. Using catalytic graphitization, graphitic materials can be manufactured at temperatures between 600° C. and 1400° C.
Recently, this method has been used to manufacture hollow graphitic nanoparticles. The hollow graphitic nanoparticles are manufactured by forming a carbon precursor on iron nanoparticles and carbonizing the precursor. The iron nanoparticles and any amorphous carbon are removed from the hollow nanoparticles by treating the material with an acid and an oxidizing agent (e.g., potassium permanganate), respectively.
One problem with treating carbon nanomaterials with acid and/or an oxidizing agent is that the acid and/or oxidizing agent can generate functional groups on the surface of the carbon nanostructures and/or other graphitic materials mixed with the carbon nanostructures. Functional groups that can be introduced by acids and oxidizing agents include carboxylate groups, carbonyl groups, hydroxyl groups, ether groups, and hydronium groups. These functional groups can significantly affect the mechanical, chemical, and electrical properties of the carbon nanomaterial.